%0 Journal Article
%T Activation of Nrf2-Regulated Glutathione Pathway Genes by Ischemic Preconditioning
%A Karen F. S. Bell
%A Jill H. Fowler
%A Bashayer Al-Mubarak
%A Karen Horsburgh
%A Giles E. Hardingham
%J Oxidative Medicine and Cellular Longevity
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/689524
%X Prophylactic pharmacological activation of astrocytic gene expression driven by the transcription factor Nrf2 boosts antioxidant defences and protects against neuronal loss in ischemia and other disease models. However, the role of Nrf2 in mediating endogenous neuroprotective responses is less clear. We recently showed that Nrf2 is activated by mild oxidative stress in both rodent and human astrocytes. Moreover, brief exposure to ischemic conditions was found to activate Nrf2 both in vivo and in vitro, and this was found to contribute to neuroprotective ischemic preconditioning. Here we show that transient ischemic conditions in vitro and in vivo cause an increase in the expression of Nrf2 target genes associated with the glutathione pathway, including those involved in glutathione biosynthesis and cystine uptake. Taken together, these studies indicate that astrocytic Nrf2 may represent an important mediator of endogenous neuroprotective preconditioning pathways. 1. Introduction 1.1. Nrf2 Is a Master Regulator of Antioxidant Gene Expression Many acute and chronic neurological disorders are associated with oxidative stress, caused by an imbalance in the production and detoxification of reactive oxygen species (ROS). Nuclear factor-erythroid 2-related factor 2 (Nrf2), a member of the capˇ°nˇ±collar transcription factor family, is a master regulator of antioxidant defense genes and drug-metabolizing enzymes [1, 2]. The binding of Nrf2 to a cisacting DNA promoter sequence, called the antioxidant response element (ARE), allows transactivation of a group of cytoprotective genes [1, 2]. Under normal conditions Nrf2 is bound to Kelch-like ECH-associated protein 1 (Keap1), and through a two-site interaction, the transcription factor is ubiquitinated by Cul3/Rbx1 and targeted for degradation [3]. However, under oxidative stress conditions the two-site interaction between Nrf2 and Keap1 is disrupted, allowing Nrf2 to evade Keap1-mediated ubiquitination and accumulate in the nucleus where it activates genes with an ARE sequence within their promoters, leading to an induction of antioxidant machinery [2]. Upregulation of the ARE-gene battery has a significant impact on the ability of the cell to withstand and survive sustained oxidative insults. Prophylactic Nrf2 activation by small molecules is protective against a host of oxidative insults in vitro, including free radical donors and oxygen glucose deprivation (OGD), as well as toxic levels of glutamate or N-methyl-D-aspartate (NMDA, [4¨C6]). Nrf2 activation in vivo is similarly protective, reducing neurotoxin or
%U http://www.hindawi.com/journals/omcl/2011/689524/